Automated test equipment (ATE) comprises apparatus operable for performing high speed testing on semiconductor devices. The testing is conducted to verify that the devices function properly during and after their development, fabrication, manufacturing and production processes. Some ATE apparatus specializes in testing memory devices, such as flash data storage (flash) and dynamic random access memory (DRAM).
To improve speed and efficiency and reduce costs associated with testing memory devices, such as flash memory devices for instance, some memory test apparatus (memory testers) implement memory core testing using a built off-chip test (BOST) configuration, in which a test head proximate to the devices under test, or DUTs, both interfaces with each of the multiple DUTs and performs a significant portion of the processing associated with testing. Such testers may comprise a component of an engineering workstation, which is typically deployed in a laboratory.
Memory testers write (input) patterns of test data signals to a plurality of DUTs. The signals are written addressably over each of an array of memory cells of the DUT. Current memory technology supports high density arrays of memory cells, which is expected to expand as the technology continues to develop. The memory tester reads a resulting output from each of the myriad DUTs, measures various test parameters relating to the test pattern and computes fast, complex algorithms to evaluate the measurements and thus characterize the DUTs.
The processing load borne by the test head is based on the size of the array of memory cells in the DUTs. The test head may have multiple test site processors (TSPS), each of which dedicated to testing a particular one of the multiple DUTs. Coupled with the speed at which the testing and related processing is conducted, these processing loads can generate considerable amounts of power within their small volumes. The heat is dissipated over a portion of their surface areas into the surrounding air or another heat sink in contact therewith.
Dissipating the heat effectively prevents excessive temperature rise within the TSP, which could otherwise cause problems executing or processing testing accurately. Some TSPS may operate best over a tightly controlled temperature range, yet may also produce a lot of heat. With higher heat capacity than gas, liquids are sometimes used to cool TSPS. For example, the TSP may be operated while bathed in an electrically insulating and chemically inert liquid coolant. As the TSP generates heat while computing test processing tasks, the heat is dissipated into the liquid coolant.
The heat transferred from the TSPS into the primary coolant bath is typically removed by subsequent transfer to another secondary liquid through the walls of a heat exchanger, or by refrigeration. However, both heat exchanger based and refrigerator based approaches to removing the heat from the liquid coolant require additional equipment, which occupies considerable space and consumes significant amounts of power, both of which may be at a premium in the laboratory in which the memory tester engineering work station may be deployed.
Moreover, noise and waste heat dissipated into the laboratory space by liquid to liquid heat exchanger based cooling systems and/or refrigeration based cooling systems may raise ambient sound and temperature levels to unacceptable values. Associated mechanical equipment such as tube and shell heat exchangers, valves, piping and pipe supports, and pumps and associated electrical power and control equipment make the heat exchanger based approach especially challenging to apply in confined, quiet office areas.